Analysis of molecular interactions involving biomolecules, such as proteins, nucleic acids, and glycans, is central to understanding biological processes and is a critical step in drug development. However, quantifying the affinity of molecular interactions is a considerable technical challenge. First, there are often a large number of variables that govern any particular biological interaction. Therefore obtaining equilibrium dissociation constants, for example, requires one to perform dozens of assays as the concentrations of various components are systematically varied, increasing the number of measurements needed in an already logistically challenging process. A second and more fundamental problem is the fact that many molecular interactions are transient in nature and exhibit nanomolar to micromolar affinities, leading to rapid loss of bound material or little bound material in the first place. These factors are problematic for high-throughput methods such as yeast two-hybrid and tandem affinity purification mass spectrometry where transient interactions are frequently missed. Protein-protein and protein-DNA binding microarrays (PBMs) are especially susceptible due to their stringent wash requirements, causing rapid loss of weakly bound material. Protein arrays have been applied to quantify ligand-ErbB receptor interactions with off-rates determined by surface plasmon resonance to be on the order of 10−4s−1. PBMs have been applied in a semiquantitative manner to transcription factor (TF) motif analysis for high affinity interactions, with off-rates on the order of 10−3 s−1.